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The fine structural changes associated with first and second generation schizogony in Eimeria necatrix were studied in experimentally infected chickens. First-generation schizonts were found in crypt epithelial cells up to 48 hr postinfection, and second generation schizonts at 68 to 120 hr. The fine structural changes observed during development were similar in the first and second generations. Invaginations of the plasma membrane ramified in the cytoplasm and divided the multinucleated schizont of E. necatrix into several lobes prior to merozoite formation. Subsequently, merozoites began forming at the surface in association with nuclei and then grew outward from the schizont. An intranuclear spindle apparatus associated with a centrocone was frequently seen in schizont nuclei prior to and during the process of merozoite formation. Numerous infoldings of host membrane were found in the parasitophorous vacuole throughout schizogony. Enlargement of the parasitized host cell and its nucleus occurred during the growth of both first and second generation schizonts.

THE popular theory that coccidiosis predisposes chickens to infections by opportunistic bacteria arising from the damaged intestine is supported by a limited number of research reports (Ott, 1937; Stafseth, 1931; Stephens et al., 1964; Tyzzer, 1937). Stephens et al. (1964) reported that in each of seven trials, Salmonella typhimurium was recovered from the internal organs of a higher percentage of chicks inoculated per os with both this bacterium and oocysts of Eimeria necatrix than from those given S. typhimurium alone. In that study, the chicks were examined 12 days after the administration of the coccidium and the first of three inoculations with S. typhimurium. The present study was conducted to further evaluate the effects of coccidiosis caused by E. necatrix upon the susceptibility of chicks to infection with S. typhimurium, and, subsequently, upon the rate of elimination of the bacterium from the internal organs. MATERIALS AND METHODS Four battery trials …

1. 1. The estimation of the packed red-cell volume by the micro-hematocrit technique proved to be a convenient method of measuring anemia in chickens infected with E. tenella or E. necatrix . 2. 2. Hematocrit measurements were more sensitive to the effects of infection with E. tenella than observations on the growth rate. 3. 3. With E. necatrix , a marked retardation of growth occurred in birds in which only a mild anemia was detectable.

When sporozoites of E. necatrix or E. brunetti are injected into the caeca of coccidia-free chickens they penetrate the caecal epithelium and initiate life-cycles which are similar to those developing in the usual sites in the small intestine. Viable oocysts of E. necatrix are produced which can be sporulated and, when given to coccidia-free chickens, produce characteristic infections in the small intestine. Possible implications of this investigation are discussed.

INTRODUCTION COCCIDOSIS persists as a major cause of serious economic loss to the poultry industry each year. Extensive research, therefore, continues in an effort to institute reliable control and preventative measures (Cuckler et al., 1956; Gardiner and McLoughlin, 1963; Peterson, 1960). Numerous chemotherapeutic agents are being employed but with varying results. Some of these drugs have proven to be very effective for the prevention of various types of coccidiosis, but their prolonged use in the poultry industry usually leads to the development of drug fast strains. Another factor of importance has been the emergence of species of coccidia that were previously considered relatively innocuous and are now definitely incriminated in the disease complex. This is evident in many instances in which a coccidiostat is controlling the more pathogenic species, i.e., Eimeria tenella, Eimeria necatrix, while economic losses still continue. Although the complex mechanisms of host-parasite relations existing in coccidiosis have …

MEGASUL is an anticoccidial compound. It is added to poultry feeds for the prevention, control or treatment of cecal and intestinal coccidiosis; i.e. Eimeria tenella and Eimeria necatrix. Although the drug has been widely used in the poultry industry for a number of years, there is very little in the literature relative to the effects of feeds that contain levels above .0125% Many of the drugs that are used for the prevention and treatment of diseases in man and animals, as well as some of those which are used for their growth promoting properties in animals, have been found to cause adverse affects under certain conditions. Drug levels other than those recommended by the manufacturer are frequently reported to cause trouble. Extended periods of drug administration even at recommended levels may result in untoward effects. Endicott et al. (1944) reported bone marrow depression and scattered hemorrhage in rats consuming diets …

SEVERAL investigators have shown sulfaquinoxaline to be an effective coccidiostatic agent against Eimeria tenella and Eimeria necatrix infections. This report deals with the effect of sulfaquinoxaline against Eimeria acervulina infection in young pullets in egg production. PROCEDURE Sixty-five White Leghorn pullets were reared under controlled conditions to keep them free of coccidial infection. At about 10 weeks of age each bird was placed in an individual laying cage. When they were laying about 50 percent egg production they were divided into 5 lots of 13 birds each. An effort was made to make an equal distribution of the birds on the basis of body weight and the time of laying the first egg. Beginning at this period of lot designation the birds were weighed individually twice each week at 3 or 4 day intervals. The pullets were fed an all-mash ration which was supplemented with oyster shell, when egg production . . .

NITROFURAZONE (NFZ; 5-nitro-2-furaldehyde semicarbazone) is an agent which has been used for the prevention and treatment of coccidiosis in chickens. The compound has also been ascribed the properties of growth promotion and bacteriostasis. Dodd and Stillman (1944) discussed Nitrofurazone and related compounds as bacteriostatic agents. These investigators found the 5-nitro group on the furan ring necessary for maximum bacteriostatic effect. Stillman and Scott (1945) considered the chemistry of Nitrofurazone and the pharmacology of the compound was studied by Kranz and Evans (1945). Activity of Nitrofurazone against experimental infections of Streptococci and Trypanosoma equiperdum was reported by Dodd (1946). Peterson and Hymas (1950) tested various levels of Nitrofurazone and other coccidiostats in chickens experimentally infected with Eimeria necatrix. These authors reported that a low level intake of Nitrofurazone resulted in almost complete prevention of coccidiosis. They observed that 0.02% of Nitrofurazone fed continuously in the mash depressed the growth of chicks. . . .

THE work of Horton-Smith (1942–43), Swales (1944–46), Hawkins (1943), Levine (1939–41), Farr and Allen (1942), Ripsom and Herrick (1945), Thorp (1947) and Seegar (1946) has shown the value of the sulfonamides in the control of cecal coccidiosis. Delaplane (1945) first reported the use of sulfaquinoxaline as a preventive against enzootic Pasteurella avicida infection in chickens. Delaplane, Batchelder and Higgins (1947) reported that 0.05 percent sulfaquinoxaline in the mash, when given four days out of eight, 50 percent of the time, was effective in preventing Eimeria tenella infection in chickens during the summer months. They also reported that 0.033 percent given continuously in the mash gave good protection against cecal coccidiosis. Further studies of the prophylactic use of sulfaquinoxaline were continued on a commercial poultry farm where 33,126 broilers were given 0.05 percent of the drug with various feeding schedules. The work was carried on for a period . . .

ALTHOUGH extensive studies have been reported on coccidiosis control in recent years, very few have dealt with incidence and geographical distribution of the various species of coccidia. Additional information would be helpful to poultry-men who must design adequate control programs against all species of economic importance. Few reports on distribution of the intestinal species, E. necatrix, have appeared within the United States. Levine (1940) reported E. necatrix present in 38% of 39 chickens examined from 33 farms from New York state. Zimmerman (1957) reported this species present on two farms in Iowa. Edgar (1958) reported a high degree of immunity in 3 and a partial immunity in 6 out of 16 flocks at 9 to 10 weeks of age from samples taken off of different farms in Alabama. These samplings give some indication of the prevalence of this species in the areas under study. Similar investigations of other areas and …

THE conditions which enable bacterial species normally confined to the intestinal tracts of chickens to invade the blood stream and internal organs have not been elucidated. Stafseth (1931) suggested that coccidia might indirectly cause leg weakness in chicks by opening avenues of entrance to bacteria normally confined to the small intestine. Tyzzer (1929) reported that the severity of coccidiosis in chickens may be increased if the birds are concurrently infected with Salmonella pullorum. Ott (1937) recovered Escherichia coli from the livers of chickens having cecal coccidiosis more frequently than from the livers of chickens not having coccidiosis, following oral administrations of this bacterium. The studies of Seidman and Arnold (1932) indicate that, in rats, degradation of the intestinal mucous membrane makes the intestine more permeable to bacteria. When the rats were sacrificed one-half hour and one hour after the administration of Salmonella typhimurium cells by stomach tube, the bacterium was…

Harisch G. , Dey-Hazra A. , Enigk K. and Schole J. 1972. Zur endokrinen Reaktion des Wirtstieres auf parasitare Infektionen. International Journal for Parasitology 2: 45–53. Rats were infected with Fasciola hepatica, Trichinella spiralis, Strongyloides ransomi, Ancylo-stoma caninum, Ascaris suum , or Trypanosoma brucei and chickens with Ascaridia galli or Eimeria necatrix , respectively. The glutathione quotient in the liver was at subnormal levels 30 min after infection, had increased values after 1 h and had subnormal values 2 h after infection or later indicating an alarm reaction of the adreno-cortical system. The reaction was unspecific although depending on the size of the stress. The glutathione quotient was not altered through peroral or intraperitoneal application of 18 per cent aqueous gelatine solution or through intraperitoneal injection of mouse blood into rats or of physiological saline into rats and chickens or through handling these animals.

IN PREVIOUS papers in this series (Turk and Stephens, 1966Turk and Stephens, 1967 a, b), we have outlined the effects upon nutrient absorption of the coccidial infection of chickens produced by a single large inoculum of sporulated oocysts. The resulting short-lived acute infections were not typical of naturally-occurring infections which usually result from ingestion of fewer coccidial oocysts over a period of several days. Therefore, a series of trials was set up to determine the effects of an infection of the anterior one-third of the small intestine induced by five daily doses of Eimeria acervulina oocysts, or the infection of the middle one-third of the small intestine induced by 5 doses of Eimeria necatrix, upon the absorption of zinc and oleic acid. PROCEDURE Commercial broiler male chicks were raised to four weeks of age in electrically heated batteries with ad libitum access to a non-medicated chick starter ration and tap water. At. . .

SUMMARY The resistance to Eimeria necalrix infection of two strains each of Light Sussex and Rhode Island Red chickens and the crosses between were studied. Differences in survival rates between pure strains within breeds was greater than differences between breeds. The resistance of crosses was higher than mid- parental values in all crosses studied suggesting that heterosis is important in determining resistance of cross chicks to E. necatrix infection. There were also differences among reciprocal crosses in survival rates indicating that maternal effects may also be important.

Although lesion scoring is a commonly accepted criterion for determining the pathogenicity of coccidial species, no previous attempt has been made to standardize and describe the scoring scale. In battery trials using pure species, the six species Eimeria tenella, E. necatrix, acervulina, E. mivati, E. maxima , and E. brunetti have been scored on a 0 to + 4 scale with descriptions of the gross pathologic changes for each score. Eimeria maxima and E. brunetti were found to be the most difficult species to score since the gross pathologic picture has been difficult to correlate with weight gains or other indications of pathogenicity. Birds from floor-pen trials infected with more than one species were also graded on a 0 to +4 scale. Four sections of the intestine (upper, middle, lower, and ceca) were each scored separately. No attempt was made to determine species, but microscopic examination of scrapings was made to confirm the presence of coccidia.

Resistance to E. necatrix induced by complete life-cycle infections was transferable from duodenum to caeca and vice versa.Complete life-cycle infections with E. tenella protected against subsequent attempts to infect with 2nd-generation merozoites. A similar experiment using E. necatrix showed a partial effect.E. necatrix gametogony-only infections did not protect against subsequent gametogony-only infections and did not protect against schizogony in the duodenum. They did suppress oocyst production resulting from entire life-cycle infections.Satisfactory oocyst production from the intra-caecal inoculation of second generation E. necatrix merozoites was not obtained.Repeated oral infections with E. tenella or E. necatrix reduced subsequent cross-infections with E. necatrix or E. tenella respectively by approximately half. Both schizogony and gametogony stages were affected.A similar result was obtained with E. tenella oocyst inoculation when previous infections were initiated by the intra-caecal injection of E. necatrix sporozoites.Oocyst production from the oral administration of E. tenella oocysts to birds previously infected with gametogony stages only of E. necatrix was much reduced but the schizogony stages of the challenge infection were not appreciably affected. Previous repeated caecal inoculation of E. necatrix merozoites did not reduce oocyst production from subsequent inoculations of E. tenella merozoites or of E. necatrix merozoites.Thanks are due to Mr P. L. Long for his interest and advice. The excellent technical assistance of Mr Brian Millard and other members of the Parasitology Department is also gratefully acknowledged.

Ulcerative enteritis (UE) was reproduced in two groups of 20, five-week old Leghorn pullets. The disease was initiated by exposure to a sublethal dose of coccidia followed on the 4th and 5th days by stress in the form of fasting and on the 4th, 5th and 6th days by inoculation with UE material obtained from Bobwhite quail which had clinical lesions of UE. When the chickens were inoculated with Eimeria brunetti or Eimeria necatrix 70% and 50% of them, respectively, developed lesions of UE.

Cytochemical studies concerning the presence and distribution of various enzymes in the tissue stages of the life cycle of Eimeria acervulina and E. necatrix have been undertaken. Acid and alkaline phosphatases as well as ATPase (pH 7·2) were found to be present in all the stages of the life cycles examined, the latter enzyme being very strong in the plastic granules of the macrogametocytes and in the inner membrane of the oocyst wall. The reaction for all three enzymes was observed in the cytoplasm but not the nucleus. Non-specific esterase and glucose-6-phosphatase were also found in all stages examined, the latter occurring in greater amounts in stages where deposition of glycogen (amylopectin) was pronounced. Succinic dehydrogenase occurred only in the second generation schizonts and merozoites of E. necatrix and in the formed oocysts of both species. No reaction for β-glucuronidase or leucine naphthylamidase was apparent in any stage, although a slight reaction for leucine naphthlyamidase was seen in the second generation merozoites of E. necatrix lying free in the intestinal lumen. The presence and distribution of these enzymes and their possible function were discussed.

PRIOR to the work of Tyzzer (1927), Johnson (1938), Levine (1938), and others, all coccidia infecting the domestic fowl were classified as Eimeria avium. Seven species of coccidia now have been identified. They are: Eimeria tenella, Eimeria acervulina, Eimeria mitis, Eimeria praecox, Eimeria maxima, Eimeria necatrix, and Eimeria hagani. Of these seven species Eimeria tenella is of the greatest economic importance, usually attacking brooder house chicks between the ages of 3 and 10 weeks. Before 1920 little was known of the control of coccidiosis, except through limitation of infection. The past two decades have witnessed many reported preventive and curative measures. In the absence of controlled experimental data, the reported “cures” may be attributed largely to a sub-fatal dose or to the careful nursing attention given infected broods during the attack. Beach and Corl (1925) tested a large number of medicinal agents and found them to be of little value . . .

THERE seems to be some feeling that young chickens are less susceptible than older chickens to infections with Eimeria necatrix. This evidently stems from the studies of Tyzzer, Theiler and Jones (1932) in which they report an experiment in which 7 of 8 birds 35 days old died of experimental infections while only 1 of 7 birds 8 days old died of the infection. The extended discussion of possible factors involved in this matter is excellent and complete and will not be repeated here. In this experiment the birds of different ages were permitted to eat uniformly infected feed for four hours after fasting overnight. This would seem to regulate the oocyst dosage by the size (volume) of the digestive tract. Obviously, the older or larger chickens ingested a larger number of oocysts than the smaller chickens, which may account for the results obtained. Since, as Tyzzer et al. (1932) . . .

The effect of Eimeria necatrix infections of the middle small intestine upon the absorption of orally administered zinc-65 has been previously reported (Turk and Stephens, 1966). The present report extends these studies to include another nutrient: oleic acid. PROCEDURE The procedures outlined in the previous report (Turk and Stephens, 1966) were followed with these modifications: 1. A capsule containing 20 μc. of I–131 labeled oleic acid (Abbott Laboratories, Oak Ridge, Tennessee) was orally administered, concurrently with a capsule containing 50 μc. of zinc-65, to each experimental bird. 2. The amount of zinc-65 and I-131 in each blood sample was determined in a well crystal scintillation detector attached to a dual channel spectrometer adjusted for the photopeaks of each isotope. 3. Sixty thousand sporulated oocysts of E. necatrix were administered orally to each bird in the infected groups. RESULTS AND DISCUSSION Table 1 summarizes the effects of E. necatrix infection …

DIRECT measurements of nutrient absorption from disease-damaged intestines in which the type, location, and severity of the damage were controlled have shown that the location of the disease damage as well as its severity and the type of nutrient under consideration are important factors in determining the amount of the nutrient absorbed. Previous work (Turk and Stephens, 1967c), using the protozoan parasite Eimeria acervulina to infect the upper half of the small intestine, has shown that absorption of iodine-131-labeled oleic acid and Zn-65 were decreased to approximately the same extent during the acute phase of the infection. However, when the infecting organism used was Eimeria necatrix, which attacks the mid-portion of the small intestine, zinc absorption (Turk and Stephens, 1966) was much more severely decreased then was oleic acid absorption (Turk and Stephens, 1967a) during the course of the infection. An infection of the ceca, produced by Eimeria tenella, affected…

Publisher Summary This chapter discusses the chemotherapy of chicken coccidiosis. Coccidiosis of the chicken can be caused by any one of nine species of parasite, either alone or in combination. Only six of the species— Eimeria acervulina , Eimeria brunetti , Eimeria maxima , Eimeria mivati , Eimeria necatrix , and Eimeria tenella are thought to be of economic significance. E. necatrix and E. tenella can give rise to spectacular outbreaks of disease, with blood-stained litter and appreciable mortality, whereas other species are more insidious in their attack. The greater part of the coccidial developmental cycle takes place in the chicken, and most attempts at control have involved the use of preventive or therapeutic medication in the host. The source of infection however, is the omnipresent oocyst, passed out at the end of the life cycle in the bird, and subsequently undergoing the process of sporulation on the ground before becoming infective to a new host. The chapter also discusses the modes of drug action and drawing attention to the possibility of inhibiting development of coccidia without actually killing the parasite. Drugs that have activity against coccidia are usually referred to as coccidiostats.

Four week-old broiler chicks were singly infected by oral administration of Eimeria acervulina, Eimeria necatrix, Eimeria brunetti, or Eimeria tenella oocysts. At intervals throughout the resulting infections, calcium absorption was determined by measurement of the amount of the oral dose of radiocalcium that appeared in the blood stream of the infected birds at intervals of 1, 4, and 8 hours post dosing. Calcium absorption was increased on the first day of all infections and was decreased on the sixth day of infections by E. acervulina, E. necatrix, and E. brunetti; but not by E. tenella. Thus, in contrast to zinc, oleic acid, protein, and certain amino acids, calcium appeared to be absorbed throughout the length of the small intestine.

Publisher Summary This chapter discusses a study analyzing site selection of coccidia in the fowl and the relationship of Eimeria Necatrix and Eimeria Tenella. In a single experiment, E. brunetti sporozoites were injected into a ligated caecum. In chickens killed on the 71st h of the infection smears taken from the caeca showed some merozoites. No organisms were evident in the open caecum of the same bird. In a control bird in which sporozoites were injected into the duodenum, numerous second generation schizonts were found in the lower small intestine but no stages were observed in the caeca. In one bird killed on the 120th h of the infection, the mucosa of the infected ligated caeca had been shed but schizonts and gametocytes were found on the edges of the remaining tissue. The control chickens that had received sporozoites via the duodenum were heavily infected in the lower small intestine but no stages were found in the caeca. The chapter highlights that this experiment needs repeating but fewer sporozoites should be injected so that less tissue damage ensues and the extent of parasitism better determined.

Freshly sporulated oocysts of Eimeria necatrix were administered to 2- and 6-week-old chickens in single doses ranging from 312 to 1,280,000 oocysts. Doses of 312 to 5000 oocysts led to small decreases in weight gain and a relatively low production of oocysts which ranged from 8 to 16 million oocysts per bird, scattered petechial hemorrhages, and small white circular colonies of schizonts were present under the serosa of the jejunum. After infection with 20,000 or more oocysts, morbidity and mortality were high with typical lesions of severe hemorrhagic enteritis. There were no survivors when the birds received 80,000 or more oocysts. Sudden death was a characteristic feature of the disease. Oocyst production and mortality were useful criteria in the recognition of low and high levels of infection, respectively. Changes in weight and packed red cell volume were of limited value in the assessment of the pathogenicity of E. necatrix . At low levels of infection four times as many oocysts were necessary to produce the same effect on weight and packed red cell volume in 6-week-old chickens as in 2-week-old chickens.

INTRODUCTION IN THE course of a routine screening of nitrofuran compounds against Eimeria tenella, nihydrazone (5-nitro-2-furaldehyde acetylhydrazone) emerged as one of the most promising of the compounds tested. Because of its relatively low toxicity and high degree of anti-coccidial activity, further investigations in batteries and on the floor were carried out to determine possible use of nihydrazone as a feed additive for the prevention of acute and chronic coccidiosis in chickens. EXPERIMENTAL PROCEDURE The anticoccidial activity of nihydrazone was investigated in a series of six experiments. The coccidia included in these studies were Eimeria tenella, Eimeria necatrix and Eimeria acervulina. The strain of E. tenella was obtained from Dr. E. Wehr, U.S.D.A., Beltsville, Maryland, E. necatrix was obtained from Dr. E. Dickinson, Oregon State University and E. acervulina was obtained from Dr. S. Kantor, Lederle Laboratories of the American Cyanamid Company. All three of the cultures were passed through birds…

AND 1951 Efficacy of 0.0055 per cent nitrofurazone fed continuously for the control of avian coccidiosis under conditions of natural infection. J. Parasit. 37 (suppl.) : 13. AND 1953 A search for drug-fast strains of Eimeria tenella. J. Parasit. 39: 268-271. HORTON-SMITH, C. AND LONG, P. L. 1952 Nitrofurazone in the treatment of caecal coccidiosis in chickens. Brit. Vet. J. 108: 47-57. PETERSON, E. H. AND HYMAS, T. A. 1950 Sulfaquinoxaline, nitrofurazone, and nitrophenide in the prophylaxis of experimental Eimeria necatrix infection. Am. J. Vet. Res. 11: 278-283. SWALES, W. E. 1950 On the chemotherapy of caecal coccidiosis (Eimeria tenella) of chickens. VII. The use of a standardized test to determine coccidiostatic properties of drugs. Canad. J. Comp. Med. 14: 269-274.

Fowl pox in chickens does not present a problem to most poultrymen, since a satisfactory vaccine is available for prevention. Serious manifestations of the infection may occur when birds not protected become infected with the fowl pox virus (3). A review of the literature did not reveal any information regarding the response to fowl pox vaccination of the heart, spleen, adrenals, or bursa of Fabricius of chickens. Significantly larger relative adrenal size and lower body weight gains were observed in chickens vaccinated with the Roakin Newcastle vaccine (5). Relative weight of the pancreas, spleen, and bursa of Fabricius were significantly larger in birds infected with Eimeria necatrix and Eimeria acervulina (7). Similar enlargement of the adrenals has been noted (2,7). Hypertrophy of the adrenal has been reported following exposure to fowl typhoid (6), avian leukosis (1), and ascarid or tuberculosis (8). The spleen has been observed to be enlarged in chicks resistant to Salmonella pullorum (9). An involution of the bursa of Fabricius was observed in young chickens vaccinated with the Roakin strain of Newcastle virus (5) and in chicks following exposure to fowl typhoid (6). The work reported here was done to determine if the heart, spleen, adrenals, or bursa of Fabricius of three strains

Waletzky, Hughes, and Brandt (1949) reported that the continuous feeding of nitrophenide in the mash at a concentration of 0.05 per cent for eight to ten days, starting on the day of inoculation or one or two days before inoculation, checked mortality from severe cecal coccidiosis in chicks. They also referred to unpublished data by themselves which indicated that nitrophenide was effective in controlling Eimeria tenella infections when administered 48 to 96 hours after inoculation; the drug was ineffective, however, when administered at time of inoculation to 48 hours after inoculation. In the same paper they presented preliminary evidence to show that nitrophenide is also effective against Eimeria necatrix. Bottorff (1950) presented data from field tests to show that the feeding of nitrophenide in the mash to chicks, from one day of age through 11 weeks, reduced mortality from cecal coccidiosis. Seeger (1950) fed nitrophenide continuously in the mash at concentrations of 0.0125 and 0.00625 per cent and reported good results. Swales (1950) fed nitrophenide continuously in the mash at 0.0125 per cent concentration, starting 24 hours before exposure to contaminated litter, and obtained little protection from cecal coccidiosis. In continuous feeding at 0.05 per cent concentration, starting at time of exposure, he got widely varying results. However, he found that the feeding of 0.1 per cent concentration for four days, starting 48 hours after exposure, resulted in a definite reduction in mortality. In a more recent paper (1951), Swales reported a reduction in mortality among birds on field tests, treated continuously with 0.0125 per cent nitrophenide mash. Peterson and Hymas (1950) found that a concentration of 0.05 per cent was necessary to suppress mortality in experimental Eimeria necatrix infection. Brackett and Bliznick (1949) reported that chicks given nitrophenide continuously for the duration of the experiment discharged fewer oocysts of Eimeria tenella than did untreated chicks, and that the percentage of sporulation of the oocysts passed by treated birds was much lower than that of the oocysts passed by untreated birds. Dickinson, Babcock, and Osebold (1951) found that continuous feeding of nitrophenide in the mash at a level of 0.05 per cent suppressed oocyst development of both cecal and intestinal coccidia, and gave protection from the disease during the period of administration of the drug.

Three trials were conducted to study the effects of Eimeria necatrix infection upon young chickens. Four-week-old chicks were inoculated with oocysts of E. necatrix and were examined periodically during the infection. An increase in erythrocyte sedimentation rate (ESR) of the infected chicks was observed on the 6th day postinoculation. ESR of the infected chicks was maximum, in relation to that of the control chicks, on the 9th or 10th day postinoculation, and returned to approximately that of the control chicks by the 16th or 18th day postinoculation. Packed erythrocyte volume was inversely related to ESR in each trial. Buffy blood coat value of the infected chicks reached a maximum in relation to that of the control chicks on the 9th day postinoculation in a trial in which the chicks suffered a severe infection, and on the 12th or 13th day postinoculation in two trials in which less severe infections were induced. The per cent light transmittance of the plasma of chicks having coccidiosis was greater than that of the plasma of control chicks throughout each trial, the difference being greatest on the 6th day postinoculation. A marked decrease in pH of the intestinal contents of the chicks was observed on the 6th and 9th days of a severe coccidial infection. The two most pathogenic species of Eimeria which cause coccidiosis in chickens are Eimeria necatrix and Eimeria tenella. While the latter has been studied extensively, relatively few reports of studies involving E. necatrix are found in the literature. E. necatrix infection was first described by Johnson (1930), but was described in more detail by Tyzzer, Theiler, and Jones (1932), and more recently by Davis (1956), and Van Doorninck and Becker (1957). Tyzzer et al. (1932) observed depression in weight gain, extensive sloughing of intestinal mucosa, and hemorrhaging into the lumen of the gut in chicks infected with E. necatrix. Davis (1956) reported that the first signs of the disease were observed toward the end of the 4th day postinfection, with deaths occurring on the 5th, 6th, and 7th days. Natt and Herrick (1955) reported that both erythrocyte count and packed erythrocyte volumes of chicks infected with E. tenella decreased about 50% during the hemorrhagic phase of cecal coccidiosis. Bierer et al. (1963) described the effects of several diseases upon blood values, but did not study coccidiosis caused by individual Eimeria species. Received for publication 17 August 1964. * Published with approval of the Director of the South Carolina Agricultural Experiment Station as Technical Contribution 500. Results of a previous study indicate that coccidiosis by E. necatrix caused an increase in erythrocyte sedimentation rate and buffy blood coat, and a decrease in packed erythrocyte volume and pH of the intestinal contents (Stephens, 1964). Since additional reports relative to effects of E. necatrix upon blood values and pH of the intestine were not found in the literature, a study was initiated to determine some of the physiological effects at various intervals during the infection of coccidiosis by E. necatrix. MATERIALS AND METHODS Three battery trials, each involving a total of 140 chicks, were conducted. Vantress X White Plymouth Rock male chicks were used in the first trial, White Plymouth Rock X White Leghorn chicks in the second, and Jaap's White Gold chicks in the third trial. A suspension of sporulated oocysts in tap water was pipetted into the crops of half the chicks used in each trial when the chicks were 4 weeks old. Each chick in the infected group received 75,000 sporulated oocysts in the first trial and 50,000 oocysts in the second and third trials. Erythrocyte sedimentation rate (ESR), packed erythrocyte volume (PEV), buffy blood coat value (BC), pH of the intestinal contents, and light transmittance of the plasma were determined periodically following administration of the coccidial oocysts. In the second and third trials, weight gains during the postinoculation period were also

The difficulty of separating Eimeria necatrix from E. tenella when the oocysts of both species are present in the ceca, led the writer to investigate the possibility of infecting chickens with merozoites. The only clear-cut evidence demonstrating the transmission of coccidial infection with merozoites was presented by Roudabush (1935) who infected rats with the merozoites of E. miyairii. Andrews' report (1927) of successful transmission of Isospora felis to a cat by feeding merozoites is open to some question since he did not eliminate the possibility of sporozoites being present along with the merozoites. Tyzzer (1929), despite repeated attempts, failed to infect chickens with E. tenella by cloacal injections of merozoites.